This invention relates to a biofeedback device for the recognition of specific frequency components encompassed in the brain wave potential and the muscle potential.
The .alpha. component of the brain wave in the frequency band of 8 to 13 Hz constitutes an index of the tranquility of mental state. With a device capable of extracting the .alpha. wave component of the brain wave and converting it to an associated audible sound, a person can promote tranquillization of his own mental state by listening to the sound and endeavoring to control his mental activity so as to increase the frequency at which this specific component is generated as sensed by the presence of the associated sound. This endeavor is generally referred to as "biofeedback therapy". Heretofore, psychiatrists and psychologists have trained their patients to improve their ability to generate such specific brain waves as a way of self-control. In this case, for the purpose of exact detection of the frequency components of the wave forms of the brain wave potential and muscle potential, the therapy has inevitably required use of a bulky amplifying apparatus in a laboratory and the patient himself has been compelled to remain at perfect rest during the therapy.
If mere extraction of the specific frequency components of the brain wave and muscle potential were sufficient for the purpose of this therapy, then the measurement could be accomplished with ample accuracy by increasing the S/N ratio to the extent of shutting off the external noise and, at the same time, the apparatus to be used could do without a bulky amplifier and could be greatly reduced in size.
Unfortunately, any attempt at exclusively extracting, through filtration, the .alpha. wave component of the frequency band of 8 to 13 Hz from the brain wave is foiled by harmonic interference caused even by the mere movement of the head which mingles into the .alpha. wave component. Even the muscle wave form which is generated by the movement of eye lids creates harmonic interference in the .alpha. wave component. Exact detection of the .alpha. wave component in the brain wave, therefore, cannot be attained by sole use of a wave filter capable of separating the wave of the frequency band of 8 to 13 Hz.
An object of the present invention is to provide a biofeedback device which permits easy recognition of the .alpha. wave component of the brain wave only.
Another object of the present invention is to provide a biofeedback device which permits easy recognition of the mental state of a subject and the condition of the subject's cephalic tension with clear distinction.